Methods for cutting bone

ABSTRACT

A method of cutting bone with a bone die cutter includes positioning complementary cutting dies on at least substantially opposing sides of a bone. At least one of the cutting dies is pressed toward the other so that the cutting dies cut a bone portion from the bone. The cut bone portion is separated from the remainder of the bone. The cut bone portion is subsequently reattached to the bone at the location from which it was removed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/360,250, filed Feb. 6, 2003, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to methods for cutting bone usingcomplementary cutting dies. The method can be used for gaining surgicalaccess to the knee cavity by performing a tibial tubercle osteotomy aspart of a minimally invasive total or partial knee arthroplasty or otherknee related surgery.

2. Related Technology

As a result of accident, deterioration, or other causes, it is oftennecessary to surgically replace all or portions of a knee joint. Jointreplacement is referred to as arthroplasty. Conventional total kneearthroplasty requires a relatively long incision that typically extendslongitudinally along the lateral side of the leg spanning across theknee joint. To allow the use of conventional techniques, instruments,and implants, the incision typically extends proximal of the knee andinto the muscular tissue. In general, the longer the incision and themore muscular tissue that is cut, the longer it takes for the patient torecover and the greater the potential for infection.

Accordingly, what is needed are minimally invasive procedures andcorresponding apparatus for accessing the knee joint to perform total orpartial knee arthroplasty.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope.

FIG. 1 is an elevated front view of a leg in a bent position;

FIG. 2 is a elevated front view of a tibia of the leg shown in FIG. 1with a portion of the tibial tuberosity removed;

FIG. 3 is an elevated side view of the tibia shown in FIG. 2;

FIG. 4 is a perspective view of a die cutter;

FIG. 5 is a perspective view of the arm assembly of the die cutter shownin FIG. 4;

FIG. 6 is an elevated front view of a guide;

FIG. 7 is a perspective view of the guide shown in FIG. 6; and

FIG. 8 is a top plan view of the guide shown in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to methods and corresponding instrumentsfor performing a tibial tubercle osteotomy to gain access to the kneecavity as part of a minimally invasive total or partial kneearthroplasty or other knee related surgery. By way of example and not bylimitation, depicted in FIG. 1 is a knee 10 having an anterior side 12.Knee 10 is flexed to about 90 degrees. A transverse incision 14,approximately 10 cm long, is made mediolaterally through the skin layeracross the midline of knee 10 proximal of the tibial tuberosity. Asdepicted in FIG. 2, the tissue is retracted exposing in part a patellarligament 18 and a tibial tuberosity 20 of a tibia 22. A portion oftibial tuberosity 20 connected to patellar ligament 18 is now elevatedsuch that patellar ligament 18 remains connected thereto.

Specifically, FIG. 2 shows a lateral view of the proximal end of tibia22. A distal portion 30 of tibial tuberosity 20 has been elevated whilea proximal portion 32 of tibial tuberosity 20 remains integral withtibia 22. Patellar ligament 18 is excised from proximal portion 30 oftibial tuberosity 20 so that the distal end of patellar ligament 18 canbe freely elevated in connection with distal portion 30 of tibialtuberosity 20. In one embodiment, distal portion 30 of tibial tuberosity20 is sized such that between about ⅓ to about ½ of the centralmediolateral width of patella ligament 18 and tibial tuberosity 20 isosteotimized from the proximal end of tibia 22. Thus about ⅓ to about ½of the distal contact surface of patellar ligament 18 remains connectedto distal portion 30 of tibial tuberosity 20.

Tibia 22 has an anterior cut surface 34. With reference to the lateralside view of tibia 22 depicted in FIG. 2, cut surface 34 includes aproximally arched undercut portion 36 formed on the distal end ofproximal portion 32 of tibial tuberosity 20. As a result of cut surface34, proximal portion 32 of tibial tuberosity 20 terminates at a distallyprojecting anterior ridge 42.

Cut surface 34 also includes a distally sloping portion 38 extendingfrom undercut portion 36 to an anterior border 40 of tibia 22. Cutsurface 34 partially bounds a pocket 35 and has a transverseconfiguration taken along a plane extending proximal to distal that issimilar to a vertically bisected heart design as depicted onconventional playing cards. In contrast to forming a smooth bisectedheart shape design, cut surface 34 can also form a sharp or slightlyrounded inside angle that is typically 90° or less.

As depicted in FIG. 3, cut surface 34 also has a substantially wedgedshaped transverse configuration taken along a plane extending anteriorto posterior. Specifically, cut surface 34 comprises a lateral side 24and an opposing medial side 26 that each slope inwardly so as tointersect at a vertical midline 28. In one embodiment, the inside angleθ between lateral side 24 and medial side 26 is in a range between about60° to about 120° with about 80° to about 100° being more preferred. Inalternative embodiments, cut surface 34 can be substantially flatextending mediolaterally or can form a rounded groove.

Elevated distal portion 30 of tibial tuberosity 20 has a cut surface 46that is complementary to cut surface 34. As will be discussed below ingreater detail, one of the benefits of the configuration of cut surfaces34 and 46 is that once the procedure is complete, distal portion 30 oftibial tuberosity 20 is easily reinserted within pocket 35. Thecomplementary mating with undercut surface 36 helps lock distal portion30 within pocket 35 as distal potion 30 is pulled proximal by patellarligament 18.

Distal portion 30 of tibial tuberosity 20 can be elevated using a numberof different techniques. By way of example and not by limitation,depicted in FIG. 4 is one embodiment of a die cutter 50 incorporatingfeatures of the present invention. Die cutter 50 comprises a housing 52having a substantially box shaped configuration. Housing 52 has a frontface 56 and an opposing back face 57 with side faces 58 and 60 extendingtherebetween. A top face 54 and an opposing bottom face 55 also extendbetween faces 56 and 57. Housing 52 bounds a chamber 62. Chamber 62communicates with the exterior through an elongated slot 64 formed onfront face 52 and an opening 66 formed on each side face 58 and 60.

A handle 68 outwardly projects from top face 54 of housing 52. Athreaded alignment bolt 69 passes through handle 68 and a portion ofhousing 52 so as to centrally project beyond front face 56 of housing52. Alignment bolt 69 threadedly engages with handle 68 and/or housing52 such that selective rotation of alignment bolt 69 facilitatesselective positioning of alignment bolt 69 beyond front face 56 ofhousing 52.

Partially disposed within chamber 62 of housing 52 are a pair oftranslating arms 70 and 72. As depicted in FIG. 5, each translating arm70 and 72 has a distal end 74 and an opposing proximal end 76. In oneembodiment of the present invention, means are provided for selectivelyadvancing at least one of the first and second translating arms 70, 72toward the other. By way of example and not by limitation, a shaft 78has threads formed along each end thereof with the threads beingoriented in opposing directions. Each translating arm 70 and 72 isthreaded onto a corresponding end of shaft 78. Accordingly, selectiverotation of shaft 78 causes translating arms 70, 72 to either movetogether or move apart. A socket 83 is formed on each end face of shaft78. Shaft 78 is selectively rotated by inserting a tool, such as a drillbit, through one of openings 66 (FIG. 4) of housing 52 and into socket83 of shaft 78. Rotation of the tool thus facilitates rotation of shaft78.

In alternative embodiments for the means for selectively advancing, itis appreciated that shaft 78 can be replaced with a variety of otherconventional threaded shaft or bolt mechanisms. Furthermore, shaft 78can be replaced with elongated levered handles or other conventionalapparatus that facilitate manual movement of translating arms 70 and 72.In yet other embodiments, it is appreciated that hydraulic, pneumatic,or electrical mechanisms can be used for movement of translating arms 70and 72.

A plurality of spaced apart rails 79 outwardly project from each side ofeach translating arm 70, 72. Rails 79 mesh with complementary rails 92formed on the interior of housing 52. The meshing of rails 79 and 92helps to ensure that translating arms 70, 72 are maintained in alignmentduring movement. Proper alignment of translating arms 70, 72 is furthermaintained by a pin 75 slidably extending through each of translatingarms 70, 72.

Returning to FIG. 4, distal end 74 of each translating arm 70, 72extends outside of chamber 62 through slot 64. Mounted at distal end 74of each translating arm 70 and 72 is an outwardly sloping head plate 80.Each head plate 80 has an interior face 81 with an undercut engagementslot 82 formed thereon. Each interior face 81 is disposed in acorresponding plane. The planes intersect so as to form an inside anglethat is substantially equal to the angle θ formed on cut surface 34.Slidably disposed within each slot 82 is a die 84. Each die 84 has abase 86 that is connected with a corresponding head plate 80 by beingslidably engaged within slot 82. As a result, dies 84 can be easilyreplaced with new dies or with dies having an alternative configuration.

A blade 88 outwardly projects from each base 86 so as to extendorthogonally from interior face 81 of the corresponding head plate 80.Each blade 88 terminates at a free sharpened edge 90. Each blade 88 andcorresponding sharpened edge 90 has a profile that is the sameconfiguration as the profile of cut surface 34 of tibial tuberosity 20previously discussed. Blades 88 are disposed so as to opposingly face atan intersecting angle. Accordingly, as shaft 78 is selectively rotated,translating arms 70, 72 move together causing sharpened edges 90 to matetogether.

During use, once tibial tuberosity 20 is exposed as discussed above, diecutter 50 is positioned such that dies 84 are positioned on the lateraland medial side of tibial tuberosity 20. The free end of bolt 69 restsagainst the anterior surface of tibial tuberosity 20 and helps tofacilitate proper positioning of dies 84. In this regard, bolt 69functions as a spacer. In alternative embodiments, bolt 69 can bereplaced with a variety of other mechanism that permit selective spacingadjustment. For example, a rod and clamp configuration can be used.

Once die cutter 50 is appropriately positioned, shaft 78 is selectivelyrotated, such as by the use of a drill, so that translating arm 70 and72 are advanced together. In so doing, the dies 84 penetrate laterallyand medially into tibial tuberosity 20. Dies 84 continue to advanceuntil distal portion 30 of tibial tuberosity 20 is separated fromproximal portion 32 thereof.

One of the benefits of using this process is that dies 84 produce veryclean cut surfaces 34 and 46 with minimal bone loss. As a result, oncethe subsequent surgical procedure is completed, distal portion 30 can befit back into pocket 35 with a close tolerance fit. It is appreciatedthat a variety of alternative configurations of die cutters can be usedfor selective die cutting of tibial tuberosity 20.

In contrast to die cutting tibial tuberosity 20, distal portion 30 oftibial tuberosity 20 can also be elevated using a saw blade. Forexample, depicted in FIGS. 6-8 is a guide 100. Guide 100 comprises acentral plate 102 having a front face 104 and an opposing back face 106.Each of faces 104 and 106 extend between opposing sides 108 and 110.Extending between front face 104 and back face 106 are a plurality ofpassageways 112.

Formed on sides 108 and 110 of central plate 102 is a first side housing114 and a second side housing 116, respectively. Each side housing 114and 116 is formed so as to project beyond front face 104 of centralplate 102. Each of side housings 114 and 116 has an inside face 118 andan opposing outside face 120. A cavity 122 extends through each of sidehousings 114 and 116 between faces 118 and 120. Removably disposedwithin cavity 122 of side housing 114 is a first template 124. A secondtemplate 126 is disposed within cavity 122 of side housing 116. Eachtemplate 124 and 126 has a substantially box-shaped configuration whichincludes an inside face 128 and an opposing outside face 130. Insideface 128 of templates 124 and 126 are each disposed in a correspondingplane. The planes intersect so as to form an inside angle that issubstantially equal to the angle θ formed on cut surface 34.

A guide slot 132 extends through each of templates 124 and 126 betweeninside face 128 and outside face 130. Each guide slot 132 has aconfiguration complementary to the profile of cut surface 34 and extendsthrough templates 124 and 126 at an orientation perpendicular to insideface 128.

During use, once tibial tuberosity 20 is exposed, front face 104 ofcentral plate 102 is biased against the anterior side of tibialtuberosity 20 such that templates 124 and 126 are disposed on thelateral and medial side thereof. Guide slots 132 are aligned with distalportion 30 of tibial tuberosity 20 to be elevated. Once guide 100 isappropriately positioned, fasteners, such as screws, nails, or the like,are passed through passageways 112 and into tibia 22 so as to securelyretain guide 100 to tibia 22. It is noted that passageways 112 aresloped such that the fasteners extending therethrough extend intoportions of tibia 22 outside of distal portion 30 which is to beelevated.

Once guide 100 is positioned in place, a saw blade 140 is passed throughguide slot 132 of template 124 from outside face 130 to inside face 128.Saw blade 140 is moved in a reciprocating manner so as to penetrate halfway into tibial tuberosity 20. Once the reciprocating saw blade 140 hascompleted passage along guide slot 132, saw blade 140 is moved over totemplate 126 and passed through the guide slot 132 thereof. The processis then repeated. Once both cuttings are performed, distal portion 30 oftibial tuberosity 20 is freely removable from the remainder of tibia 22.The fasteners are then removed along with guide 100. As with die cutters50, it is appreciated that guide 100 can come in a variety ofalternative configurations.

As previously mentioned, once distal portion 30 of tibial tuberosity 20is elevated, patellar ligament 18 is retracted proximally, therebyexposing the knee joint. Once the knee joint is exposed, any number ofknee related surgical procedures, such as total or partial kneearthroplasty, can be performed. Referring back to FIG. 2, uponcompletion of the surgical procedure, patellar ligament 18 is securedback in place by inserting distal portion 30 of tibial tuberosity 20back into pocket 35. As a result of undercut portion 36, distal portion30 of tibial tuberosity 20 is self-locking within pocket 35. If desired,however, various types of conventional bone anchors can be used tofurther secure distal portion 30 of tibial tuberosity 20 within pocket35.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A method of cutting bone with a bone die cutter, the methodcomprising: positioning complementary cutting dies on at leastsubstantially opposing sides of a bone; pressing at least one of thecutting dies toward the other so that the cutting dies cut a boneportion from the bone; separating the cut bone portion from the bone;and reattaching the cut bone portion to the bone.
 2. A method as recitedin claim 1, wherein the act of separating the cut bone portion forms arecessed pocket on the bone, the cut bone portion being reattached intothe recessed pocket.
 3. A method as recited in claim 1, wherein therecessed pocket includes an undercut portion.
 4. A method as recited inclaim 1, further comprising the act of performing a surgical procedurebetween the acts of separating and reattaching.
 5. A method as recitedin claim 1, wherein the cutting dies are positioned on opposing lateraland medial sides of a tibial tubercle such that the cut bone portioncomprises at least a portion of the tibial tubercle.
 6. A method asrecited in claim 5, further comprising performing a total kneearthroplasty or a partial knee arthroplasty between the steps ofseparating and reattaching.
 7. A method as recited in claim 1, whereinthe cutting dies are positioned on opposing sides of a distal portion ofa tibial tubercle such that the separated cut bone portion comprises thedistal portion of the tibial tubercle while a proximal portion of thetibial tubercle remains attached to the tibia.
 8. A method as recited inclaim 7, wherein the distal portion of the tibial tubercle is separatedfrom the tibia so that at least a portion of a patella ligament remainsattached to the distal portion of the tibial tubercle.
 9. A method asrecited in claim 8, wherein the distal portion of the tibial tubercle isseparated from the tibia so that a recessed undercut pocket is at leastpartially formed on the proximal portion of the tibial tubercle.
 10. Amethod as recited in claim 1, wherein each of the dies has a bladeprojecting therefrom, the act of positioning the complementary cuttingdies comprising positioning the dies so that the blades intersect at anangle when the blades are brought together.
 11. A method as recited inclaim 1, wherein each of the dies has a transverse cross sectionalconfiguration that corresponds substantially to the contour of anexterior surface of a vertically bisected heart design.
 12. A method asrecited in claim 1, wherein the step of positioning complementarycutting dies comprises positioning a die cutter adjacent to the bone,the die cutter comprising a housing having a pair of translation armsextending therefrom, each cutting die being disposed at the end of acorresponding translation arm.